Nickel electroplating composition and process

ABSTRACT

A process for the production of semi-bright electrodeposits of nickel and nickel alloys containing at least 80 percent nickel wherein the electroplating bath used is an aqueous solution containing at least one nickel salt and brightening and/or leveling amounts of a propylene oxide adduct of propargyl alcohol and a coumarin material. In a preferred embodiment, the electroplating bath also contains butyne diol.

United States Patent 1191 Klein et al.

[ 51 March 6, 1973 1 NICKEL ELECTROPLATING COMPOSITION AND PROCESS [75] Inventors: Roy W. Klein, St. Clair Shores; Robert A. Tremmel, Woodhaven;

Richard J. Clauss, Allen Park, all of Mich.

[73] Assignee: Oxy Metal Finishing Corporation,

Warren, Mich.

[22] Filed: Dec. 11, 1970 [21] Appl. No.: 97,346

OTHER PUBLICATIONS Metal Finishing, p. 43, Nov. 1969.

Primary Examiner-G. L. Kaplan Attorney-Stanley H. Lieberstein and William J. Schramm [57] ABSTRACT A process for the production of semi-bright electrodeposits of nickel and nickel alloys containing at least 80 percent nickel wherein the electroplating bath used is an aqueous solution containing at least one nickel salt and brightening and/or leveling amounts of a propylene oxide adduct of propargyl alcohol and a coumarin material. In a preferred embodiment, the electroplating bath also contains butyne diol.

10 Claims, No Drawings NICKEL ELECTROPLATING COMPOSITION AND PROCESS This invention relates to an improved composition and process for the electrodeposition of metal and more particularly it relates to improved composition and process for the formation of semi-bright electrodeposits of nickel and nickel alloys.

The use of coumarin as an additive in Watts type nickel electroplating baths, to produce soft, ductile, lustrous deposits with excellent leveling is well known. It is further known that the degree of leveling obtained is, in general, proportional to the concentration of coumarin in the plating bath, at least within concentration ranges of about 0.05 to 0.3 grams per liter.

Generally, however, the higher concentrations of coumarin which produce the best leveling, are not used, since the degradation products which develop as the plating bath is electrolyzed are formed at a rate proportional to the concentration of the coumarin which is present. Thus, a high concentration of coumarin gives the best leveling but also the highest rate of formation of degradation products, which products are generally melilotic acid. These degradation products are objectionable in that they can cause uneven, dull gray areas which are not readily brightened by a subsequent bright nickel deposit; they reduce the leveling obtained from a given concentration of coumarin in the plating bath; and they can reduce the beneficial mechanical properties of the nickel electrodeposits.

l-leretofore, it has been proposed to overcome the undesirable effects of the coumarin degradation products by the use of aldehydes, such as formaldehyde and chloral hydrate. This use of these aldehydes has, however, had certain limitations since high concentrations of these materials not only lower the ductility of the nickel electrodeposit but also appreciably reduce the leveling action of the coumarin. It has further been proposed, in US. Pat. No. 3,414,491, to overcome the difficulty encountered in using coumarin as an additive in nickel plating baths by including in the baths an ethylene oxide adduct of an acetylenic compound. Although this technique has been helpful in overcoming the problems encountered in the use of coumarin, these ethylene oxide adducts have produced problems of their own, particularly in their preparation. In this regard, it is to be noted that the safe inhalation level of ethylene oxide is relatively low, while mixtures of ethylene oxide and air are explosive in substantially all proportions. Additionally, the reaction to form these adducts must be carried out in a closed reaction vessel under pressure. There is, therefore, not only a considerable health and safety hazard in the production of these adducts, but also, undesirable cost and complexity in the equipment required.

It is, therefore, an object of the present invention to provide an improved process for the production of bright electrodeposits of nickel and nickel-cobalt alloys containing at least 80 percent nickel.

A further object of the present invention is to provide an improved electroplating bath in which bright nickel and nickel-cobalt alloy electroplates may be deposited.

Another object of the present invention is to provide an improved additive composition for use in electroplating baths for the deposition of nickel and nickelcobalt alloy electroplates.

These and other objects will become apparent to those skilled in the art from the description of the invention which follows.

Pursuant to the above objects, the present invention includes a plating bath for the electrodeposition of nickel which comprises an aqueous solution of at least one nickel salt and brightening and/or leveling amounts of a propylene oxide adduct of propargyl alcohol and a coumarin material, as additives. Additionally, in a most preferred embodiment, the bath will also contain butyne diol. From this bath, there is electrodeposited a semi-bright, ductile nickel plate having excellent leveling properties.

More specifically, in the practice of the present invention, the electroplating baths used are aqueous solutions containing one or more nickel salts. Typically, such baths may be prepared by dissolving nickel chloride and/or nickel sulfate and boric acid in water.

Other nickel electroplating baths based on nickel sulfate, nickel chloride, nickel formate, nickel sulfamate, nickel fluoroborate, or the like, as the nickel salt dissolved in the aqueous acidic solvent, may also be used. Additionally, the electroplating baths of the present invention may also contain one or more cobalt salts, of the same or similar type as the nickel salts have been indicated above. Where the electroplating baths used contain cobalt salts in addition to the nickel salts, the relative amount ofthese should be such that the resulting nickel-cobalt alloy electroplate produced contains at least about percent nickel.

These nickel electroplating baths will contain brightening and/or leveling amounts of a propylene oxide adduct of propargyl alcohol and a coumarin compound and, in a preferred embodiment, also butyne diol. By brightening" and leveling amounts, it is intended that each of these materials, when used, will be present in the electroplating bath in amounts such that the combination will be sufficient to promote the formation of a semi-bright, ductile and self-leveling nickel electrodeposit.

The propylene oxide adducts of propargyl alcohol which are used have the formula:

in which n is a number from 1 to 3. Typically, these adducts will be present in the electroplating bath in amounts within the range of about 1 to 20 milligrams per liter, with amounts within the range of about 2 to 10 milligrams per liter being preferred.

It is to be appreciated, that with respect to the coumarin compound or material, in addition to coumarin itself, which is the most preferred, various substituted coumarins may also be used, such as 3-chlorocoumarin, 6-chlorocoumarin, 3-bromocoumarin, 3-acetyl coumarin, 7-hydroxy ethyl coumarin, S-methoxy coumarin, 7-ethoxycoumarin, 4,8-dimethyl coumarin, coumarin, 7 oxypropanesulfonic acid and the like. Typically, the coumarin or substituted coumarin compounds are present in the electroplating baths in I amounts within the range of about 0.025 to 0.5 grams per liter, with amounts within the range of about 0.05 to 0.3 grams per liter being preferred.

Although the combination of the propylene oxide adduct of propargyl alcohol with the coumarin compound overcomes the adverse effects of the coumarin degradation products and results in a consistantly semibright deposit, it has been found that as the electroplating bath is used over an extended period of time, there is a gradual decrease in the leveling properties, for a given concentration of coumarin. This decrease in leveling is minimized by also including butyne diol in the bath, as an additional additive. In this manner, without increasing the coumarin concentration, a semibright nickel electrodeposit, having excellent leveling, is consistently produced. Accordingly, in its most preferred embodiment, the electroplating bath of the present invention will typically contain from about 3 to 60 milligrams/liter butyne diol, with amounts of from about 10 to 40 milligrams/liter being preferred.

It is to be noted, however, that although the amounts of the three additive components set forth above are typical of the amounts which may be used, this is not to say that amounts of these components which are outside of these ranges may not be used. Rather, it is intended that although for many typical operations of the process of the present invention these amounts have been found to be preferred, in many instances, amounts which are both greater than and less than those which have been specifically recited will also produce satisfactory results. In this regard, it is to be appreciated that the specific amount of each of these additive components which is used will, of course, depend upon the particular amounts of the other components which are utilized. a

In formulating the electroplating baths for use in the method of the present invention, an aqueous acidic solution is formed containing the desired nickel or nickel and cobalt salts. Typically these electroplating baths will have a pH within the range of about 3 to 4.5 and, depending upon the particular nickel salts used, will contain the nickel salts in amounts within the range of about 200 to 400 grams per liter. Where cobalt salts are also present in the electroplating baths, these will typically be present in amounts within the range of about 10 to 30 grams per liter, depending upon the particular salts used as well as the amount of the nickel salt which is present. In the most preferred plating baths, which will also contain boric acid, this material is desirably present in amounts within the range of about 30 to 60 grams per liter. Additionally, the additive components are included in the electroplating bath in the amounts which have been indicated hereinabove.

In the operation of the process of the present invention, the electroplating solutions will typically be used at a temperature within the range of about 45 to 63 degrees centigrade. In general, agitation of the solution, either by air agitation, cathode rod agitation, mechanical agitation or the like, is preferred. Although with the electroplating baths of the present invention, semi-bright nickel electrodeposits are obtained over a wide current density range, e.g., 5 to 150 amps per square foot the typical average current densities used in the operation of the process are within the range of about 25 to 50 amps per square foot, with plating times of from about to 60 minutes.

When operating in this manner, excellent semibright, ductile deposits of nickel and nickel-alloys containing at least 80 percent nickel are obtained, which electrodeposits have excellent leveling characteristics. Moreover, it is found that with the combined use of the propylene oxide-propargyl alcohol adduct and the butyne diol, with the coumarin material, the adverse effects of the melilotic acid degradation product of coumarin are overcome, without the formation of other adverse degradation products and maximum leveling is obtained even with high concentrations of melilotic acid. Thus, although normally, the coumarin degrada tion products will decrease the brightness and leveling obtained from a given concentration of coumarin, in a proportion to the melilotic acid concentration, thus requiring the use of greater amounts of coumarin to maintain the leveling, by the use of these two additional additives the concentration of coumarin may be maintained at a consistent level even when appreciable amounts of melilotic acid are present, while still obtaining excellent brightness and leveling results. It is further found that by the use of the propylene oxide adduct, rather than the ethylene oxide material, there is an appreciable reduction in the health and safety hazards encountered in the preparation of this adduct, as well as a simplification of the preparation process. In this regard it is to be noted that the safe inhalation level of propylene oxide is at least twice that of ethylene oxide while the range of concentrations of mixtures in air which are explosive is less than one third that of ethylene oxide. Additionally, unlike ethylene oxide, the preparation of the adduct can be carried out at atmospheric pressure.

In order that those skilled in the art may better understand the present invention and the manner in which it may be practiced, the following specific examples are given. In these examples, unless otherwise indicated, parts and percent are by weight and temperatures are in degrees centigrade. It is to be appreciated, however, that these examples are merely exemplary of the present invention and are not to be taken as a limitation thereof.

EXAMPLE 1 An aqueous electroplating bath was formulated containing the following components in the amounts indicated:

290 grams/liter 38 grams/liter 42 grams/liter To this bath, which was operated at a pH of 3 .74.2 and a temperature of -58 C. with air agitation, was added 0.15 grams/liter of coumarin. Upon electroplating for 20 minutes at an average current density of 40 amps/ft there was obtained from the bath a uniformly semi-bright nickel electrodeposit having excellent leveling.

EXAMPLE 2 The electroplating bath of Example I was electrolyzed for the equivalent of ampere hours per gallon to produce an appreciable concentration of degradation products, primarily melilotic acid. The coumarin concentration was adjusted to 0.15 grams/liter and upon electroplating for 20 minutes at an average current density of 40 amps/ft as in Example I, there was obtained a non-uniformly semi-bright nickel electro-deposit which had some darkness in the low current density areas. Additionally, the leveling of the deposit had declined, from that obtained in the previous Example, to only a moderate level. Upon adding 5 milligrams/liter of the monopropylene oxide adduct of propargyl alcohol to the bath and continuing the electroplating under the same conditions, there was obtained a uniformly semi-bright nickel electrodeposit, having a bright or clean low current density area.

EXAMPLE 3 To the electroplating bath of Example 2 there was added, in addition to the propargyl alcohol adduct, 25 milligrams/liter of butyne diol. Upon electroplating a steel panel under the same conditions of time and current density, there was obtained a nickel electrodeposit which was not only uniformly semi-bright with a bright low current density area but in which the leveling was restored to a high level which was equal to that obtained in Example 1.

From the above results, it is seen that although coumarin alone initially gives good brightening and leveling, as the bath is operated and there is a build-up of the melilotic acid degradation products, both of these properties are decreased. By the addition of the propylene) oxide propargyl alcohol adduct, the brightening is restored, while the further addition of the butyne diol restores the leveling, while still maintaining the same coumarin concentration.

While there have been described various embodiments of the invention, the compositions and methods described are not intended to be understood as limiting the scope of the invention as it is realized that changes therewithin are possible and it is further intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same or equivalent manner, it being intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

l. A plating bath for the electrodeposition of nickel which comprises an aqueous acidic solution of at least one nickel salt and, as additives, a coumarin compound and a propylene oxide adduct of propargyl alcohol, containing one to three moles of oxide per mole of alcohol, said adduct present in an amount ranging from about 2 to mg/l, said additives being present in the plating bath in amounts such that the combination thereof produces a semi-bright ductile, self-leveling nickel deposit.

2. The plating bath as claimed in claim 1 which also contains butyne diol, as an additional additive, in amounts such that decreases in the leveling properties of the nickel deposit are minimized.

3. The plating bath as claimed in claim 2 in which the coumarin compound is present in an amount of from about .025 to 0.5 grams per liter, the propylene oxide propargyl alcohol adduct is present in an amount of from about 2 to 10 milligrams per liter and the butyne diol is present in an amount of from about 3 to 60 milligrams per liter.

4. The plating bath as claimed in claim 3 wherein the coumarin compound is coumarin, and the propylene oxide adduct of propargyl alcohol has the formula:

HC 5 CCH (OC H ),,OH

in which n is a number from 1 to 3.

5. The plating bath as claimed in clalm 4 1n Wl'llCh the coumarin is present in an amount of from about 0.05 to 0.3 grams per liter, the propylene oxide-propargyl alcohol adduct is present in an amount of from about 2 to 10 milligrams per liter and the butyne diol is present in an amount of from about 10 to 40 milligrams per liter.

6. A process for producing semi-bright nickel deposits which comprises electrodepositing nickel on a base from the electroplating bath as claimed in claim 1.

7. The process as claimed in claim 6 wherein the plating bath used also contains butyne diol, as an additional additive, in amounts such that decreases in the leveling properties of the nickel deposit are minimized.

8. The process as claimed in claim 7 wherein the coumarin compound is coumarin and the proplyene oxide adduct of propargyl alcohol has the formula:

wherein n is a number from 1 to 3.

9. The process as claimed in claim 8 wherein the coumarin is present in an amount of from about 0.05 to 0.3 grams per liter, the propylene oxide-propargyl alcohol adduct is present in an amount of from about 2 to 10 milligrams per liter and the butyne diol is present in an amount of from about 10 to 40 milligrams per liter.

10. The process as claimed in claim 7 wherein the plating bath contains the coumarin compound in an amount of from about 0.025 to 0.5 grams per liter, the propylene oxide adduct of propargyl alcohol in an amount of from about 2 to 10 milligrams per liter and the butyne diol in an amount of from about 3 to 60 milligrams per liter. 

1. A plating bath for the electrodeposition of nickel which comprises an aqueous acidic solution of at least one nickel salt and, as additives, a coumarin compound and a propylene oxide adduct of propargyl alcohol, containing one to three moles of oxide per mole of alcohol, said adduct present in an amount ranging from about 2 to 10 mg/l, said additives being present in the plating bath in amounts such that the combination thereof produces a semi-bright ductile, self-leveling nickel deposit.
 2. The plating bath as claimed in claim 1 which also contains butyne diol, as an additional additive, in amounts such that decreases in the leveling properties of the nickel deposit are minimized.
 3. The plating bath as claimed in claim 2 in which the coumarin compound is present in an amount of from about .025 to 0.5 grams per liter, the propylene oxide - propargyl alcohol adduct is present in an amount of from about 2 to 10 milligrams per liter and the butyne diol is present in an amount of from about 3 to 60 milligrams per liter.
 4. The plating bath as claimed in claim 3 wherein the coumarin compound is coumarin, and the propylene oxide adduct of propargyl alcohol has the formula: HC*C-CH2(OC3H6)nOH in which n is a number from 1 to
 3. 5. The plating bath as claimed in claim 4 in which the coumarin is present in an amount of from about 0.05 to 0.3 grams per liter, the propylene oxide-propargyl alcohol adduct is present in an amount of from about 2 to 10 milligrams per liter and the butyne diol is present in an amount of from about 10 to 40 milligrams per liter.
 6. A process for producing semi-bright nickel deposits which comprises electrodepositing nickel on a base from the electroplating bath as claimed in claim
 1. 7. The process as claimed in claim 6 wherein the plating bath used also contains butyne diol, as an additional additive, in amounts such that decreases in the leveling properties of the nickel deposit are minimized.
 8. The process as claimed in claim 7 wherein the coumarin compound is coumarin and the proplyene oxide adduct of propargyl alcohol has the formula: HC*C-CH2(OC3H6)nOH wherein n is a number from 1 to
 3. 9. The process as claimed in claim 8 wherein the coumarin is present in an amount of from about 0.05 to 0.3 grams per liter, the propylene oxide-propargyl alcohol adduct is present in an amount of from about 2 to 10 milligrams per liter and the butyne diol is present in an amount of from about 10 to 40 milligrams per liter. 